C# Winforms: The controls of a form are not displayed

I have a problem that I simply cannot solve. The controls of a form are not displayed. Where could the error be? Unfortunately, I could not find any solutions here. I would be grateful if one of the professionals here could help me.

Form:

using System;
using System.Drawing;
using System.Windows.Forms;

namespace Custom_Messagebox
{
    public partial class MessageBox_1 : Form
    {
        private void EXIT_btn_MouseHover(object sender, EventArgs e)
        {
            EXIT_btn.BackgroundImage = Custom_Messagebox.Properties.Resources.exit_over;
        }
        private void EXIT_btn_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void EXIT_btn_MouseDown(object sender, MouseEventArgs e)
        {
            EXIT_btn.BackgroundImage = Custom_Messagebox.Properties.Resources.exit_down;
        }


        private void MessageBox_1_Load(object sender, EventArgs e)
        {
        }


    }
}

Designer

namespace Custom_Messagebox
{
    partial class MessageBox_1
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.EXIT_btn = new System.Windows.Forms.Button();
            this.MessageBox_1_title = new System.Windows.Forms.Label();
            this.Message_lbl = new System.Windows.Forms.Label();
            this.SuspendLayout();
            // 
            // EXIT_btn
            // 
            this.EXIT_btn.AutoSizeMode = System.Windows.Forms.AutoSizeMode.GrowAndShrink;
            this.EXIT_btn.BackgroundImage = global::Custom_Messagebox.Properties.Resources.exit;
            this.EXIT_btn.BackgroundImageLayout = System.Windows.Forms.ImageLayout.Center;
            this.EXIT_btn.Location = new System.Drawing.Point(503, 6);
            this.EXIT_btn.Name = "EXIT_btn";
            this.EXIT_btn.Size = new System.Drawing.Size(25, 23);
            this.EXIT_btn.TabIndex = 0;
            this.EXIT_btn.UseVisualStyleBackColor = true;
            this.EXIT_btn.Click += new System.EventHandler(this.EXIT_btn_Click);
            this.EXIT_btn.MouseDown += new System.Windows.Forms.MouseEventHandler(this.EXIT_btn_MouseDown);
            this.EXIT_btn.MouseHover += new System.EventHandler(this.EXIT_btn_MouseHover);
            // 
            // MessageBox_1_title
            // 
            this.MessageBox_1_title.AutoSize = true;
            this.MessageBox_1_title.BackColor = System.Drawing.Color.Transparent;
            this.MessageBox_1_title.Font = new System.Drawing.Font("Microsoft Sans Serif", 8.25F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.MessageBox_1_title.Location = new System.Drawing.Point(22, 11);
            this.MessageBox_1_title.Name = "MessageBox_1_title";
            this.MessageBox_1_title.Size = new System.Drawing.Size(32, 13);
            this.MessageBox_1_title.TabIndex = 1;
            this.MessageBox_1_title.Text = "Titel";
            // 
            // Message_lbl
            // 
            this.Message_lbl.AutoSize = true;
            this.Message_lbl.BackColor = System.Drawing.Color.Transparent;
            this.Message_lbl.Location = new System.Drawing.Point(55, 64);
            this.Message_lbl.Name = "Message_lbl";
            this.Message_lbl.Size = new System.Drawing.Size(50, 13);
            this.Message_lbl.TabIndex = 2;
            this.Message_lbl.Text = "Message";
            // 
            // MessageBox_1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.AutoSizeMode = System.Windows.Forms.AutoSizeMode.GrowAndShrink;
            this.BackgroundImage = global::Custom_Messagebox.Properties.Resources.weave;
            this.BackgroundImageLayout = System.Windows.Forms.ImageLayout.None;
            this.ClientSize = new System.Drawing.Size(550, 300);
            this.Controls.Add(this.Message_lbl);
            this.Controls.Add(this.MessageBox_1_title);
            this.Controls.Add(this.EXIT_btn);
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
            this.MaximizeBox = false;
            this.Name = "MessageBox_1";
            this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
            this.Text = "MessageBox_1";
            this.TransparencyKey = System.Drawing.Color.Red;
            this.Load += new System.EventHandler(this.MessageBox_1_Load);
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.Button EXIT_btn;
        private System.Windows.Forms.Label MessageBox_1_title;
        private System.Windows.Forms.Label Message_lbl;
    }
}